This invention relates to a method for controlling the temperature of an appliance and, in particular, to a method of controlling the temperature of an appliance which is heated by a burner.
In food preparation and sanitation applications it is desirable to maintain the temperature of the appliance constant. For appliances heated by a burner this typically requires a presence of a user to manually adjust the output of the burner though the rotation of a control knob. This may be labor intensive and inconvenient. To eliminate the need for manual adjustment to the output of the burner, some appliances are provided with thermostatically controlled fuel valves which maintain or restrict the flow of fuel to the burner based on the temperature of the appliance. However, these appliance may also require a constant flow of fuel to the burner to maintain a flame. This is both expensive and wasteful.
To conserve fuel some appliances operate on a flame on/flame out basis. When the temperature of the appliance is greater than a maximum threshold temperature the flame is extinguished. When the temperature of the appliance is less than a minimum threshold temperature the flame is ignited. For example, in United States Patent Application Publication No. US 2006/0172238 to Cook, there is disclosed a method for controlling a heater which comprises turning a pilotless igniter on for a first period of time and opening a fuel source valve whenever the temperature is less than or equal to a low temperature setting, and closing the fuel source valve whenever the temperature is greater than or equal to a high temperature setting or a flame sensor indicates that the flame has gone out.
Since the method disclosed by Cook is, at least in part, dependent on the presence or absence of a flame it may be limiting because the absence of a flame when the temperature of the heater to greater than the low temperature setting, but less than the high temperature setting, may result in the heater being shut down. There is therefore a need for an improved method of controlling the temperature of an appliance.